STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 833 



hind with the duodenum, the commencement of which is indicated 

 by the opening of the bile duct. 



The liver is the first-formed alimentary gland, and is already 

 a compact body before the larva is hatched. We have nothing 

 to say with reference to its development, except that it exhibits 

 the same simple structure in the embryo that it does in the 

 adult. 



A more interesting glandular body is the pancreas. It has 

 already been stated that in the adult we have recognized a small 

 body which we believe to be the pancreas, but that we were 

 unable to study its histological characters. 



In the embryo there is a well-developed pancreas which 

 arises in the same position and the same manner as in those 

 Vertebrata in which the pancreas is an important gland in the 

 adult. 



We have first noticed the pancreas in a stage shortly after 

 hatching (Plate 40, fig. 6i,/.). It then has the form of a funnel- 

 shaped diverticulum of the dorsal wall of the duodenum, imme- 

 diately behind the level of the opening of the bile duct. From 

 the apex of this funnel numerous small glandular tubuli soon 

 sprout out. 



The similarity in the development of the pancreas in Lepi- 

 dosteus to that of the same gland in Elasmobranchii is very 

 striking 1 . 



The pancreas at a later stage is placed immediately behind 

 the end of the liver in a loop formed by the pyloric section of the 

 stomach (Plate 40, fig. 62, /.). During larval life it constitutes a 

 considerable gland, the anterior end of which partly envelopes 

 the bile duct (Plate 40, fig. 63,/.). 



Considering the undoubted affinities between Lepidosteus and 

 the Teleostei, the facts just recorded with reference to the 

 pancreas appear to us to demonstrate that the small size and 

 occasional absence (?) of this gland in Teleostei is a result of the 

 degeneration of this gland ; and it seems probable that the 

 pancreas will be found in the larvae of most Teleostei. These 

 conclusions render intelligible, moreover, the great development 

 of the pancreas in the Elasmobranchii. 



1 Vide F. M. Balfour, "Monograph on Development of Elasmobranch Fishes," 

 p. 226 [This edition, No. X., p. 454]. 



